Method for power headroom reporting and device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for power headroom reporting in the wireless communication system, the method comprising: obtaining information related to a power headroom (PH) for the second BS; obtaining PH of activated cells of the UE; and transmitting, to a first BS, the information related to the PH for the second BS and the PH of activated cells of the UE.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for power headroom reporting and a devicetherefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARM)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method and device for a method for power headroom reporting. Thetechnical problems solved by the present invention are not limited tothe above technical problems and those skilled in the art may understandother technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for operating by an apparatus in wireless communication system,the method comprising; obtaining information related to a power headroom(PH) for the second BS; obtaining PH of activated cells of the UE; andtransmitting, to a first BS, the information related to the PH for thesecond BS and the PH of activated cells of the UE.

In another aspect of the present invention provided herein is anapparatus in the wireless communication system, the apparatuscomprising: an RF (radio frequency) module; and a processor configuredto control the RF module, wherein the processor is configured to obtaininformation related to a power headroom (PH) for the second BS, toobtain PH of activated cells of the UE, and to transmit to a first BS,the information related to the PH for the second BS and the PH ofactivated cells of the UE.

Preferably, wherein the information comprises a ratio of a PH for thesecond BS to a PH for the first BS.

Preferably, wherein the information comprises a ratio of a PH for thefirst BS to the PH of activated cells of the UE.

Preferably, wherein the information comprises scheduling information forthe second BS.

Preferably, wherein the scheduling information indicates whether the UEreceived the UL grant for the second BS or not.

Preferably, wherein the scheduling information indicates whether the UEtransmits the PH of the second BS to the second BS or not′.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, power headroom reporting can beefficiently performed in a wireless communication system. Specifically,the UE can report power headroom to each base station efficiently indual connectivity system.

It will be appreciated by persons skilled in the art that that theeffects achieved by the present invention are not limited to what hasbeen particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIG. 5 is a diagram for carrier aggregation;

FIG. 6 is a conceptual diagram for dual connectivity between a MasterCell Group (MCG) and a Secondary Cell Group (SCG);

FIG. 7a is a conceptual diagram for C-Plane connectivity of basestations involved in dual connectivity, and FIG. 7b is a conceptualdiagram for U-Plane connectivity of base stations involved in dualconnectivity;

FIG. 8 is a conceptual diagram for radio protocol architecture for dualconnectivity;

FIG. 9 is a diagram for a general overview of the LTE protocolarchitecture for the downlink;

FIG. 10 is a diagram for signaling of buffer status and power-headroomreports;

FIG. 11 is a conceptual diagram for one of radio protocol architecturefor dual connectivity;

FIG. 12 is a conceptual diagram for a problematic case in dualconnectivity;

FIGS. 13 and 14 are conceptual diagrams for power headroom reportingaccording to embodiments of the present invention; and

FIG. 15 is a block diagram of a communication apparatus according to anembodiment of the present invention.

BEST MODE

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of an.Internet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a diagram for carrier aggregation.

Carrier aggregation technology for supporting multiple carriers isdescribed with reference to FIG. 5 as follows. As mentioned in theforegoing description, it may be able to support system bandwidth up tomaximum 100 MHz in a manner of bundling maximum 5 carriers (componentcarriers: CCs) of bandwidth unit (e.g., 20 MHz) defined in a legacywireless communication system (e.g., LTE system) by carrier aggregation.Component carriers used for carrier aggregation may be equal to ordifferent from each other in bandwidth size. And, each of the componentcarriers may have a different frequency band (or center frequency). Thecomponent carriers may exist on contiguous frequency bands. Yet,component carriers existing on non-contiguous frequency bands may beused for carrier aggregation as well. In the carrier aggregationtechnology, bandwidth sizes of uplink and downlink may be allocatedsymmetrically or asymmetrically.

Multiple carriers (component carriers) used for carrier aggregation maybe categorized into primary component carrier (PCC) and secondarycomponent carrier (SCC). The PCC may be called P-cell (primary cell) andthe SCC may be called S-cell (secondary cell). The primary componentcarrier is the carrier used by a base station to exchange traffic andcontrol signaling with a user equipment. In this case, the controlsignaling may include addition of component carrier, setting for primarycomponent carrier, uplink (UL) grant, downlink (DL) assignment and thelike. Although a base station may be able to use a plurality ofcomponent carriers, a user equipment belonging to the corresponding basestation may be set to have one primary component carrier only. If a userequipment operates in a single carrier mode, the primary componentcarrier is used. Hence, in order to be independently used, the primarycomponent carrier should be set to meet all requirements for the dataand control signaling exchange between a base station and a userequipment.

Meanwhile, the secondary component carrier may include an additionalcomponent carrier that can be activated or deactivated in accordancewith a required size of transceived data. The secondary componentcarrier may be set to be used only in accordance with a specific commandand rule received from a base station. In order to support an additionalbandwidth, the secondary component carrier may be set to be usedtogether with the primary component carrier. Through an activatedcomponent carrier, such a control signal as a UL grant, a DL assignmentand the like can be received by a user equipment from a base station.Through an activated component carrier, such a control signal in UL as achannel quality indicator (CQI), a precoding matrix index (PMI), a rankindicator (RI), a sounding reference signal (SRS) and the like can betransmitted to a base station from a user equipment.

Resource allocation to a user equipment can have a range of a primarycomponent carrier and a plurality of secondary component carriers. In amulti-carrier aggregation mode, based on a system load (i.e.,static/dynamic load balancing), a peak data rate or a service qualityrequirement, a system may be able to allocate secondary componentcarriers to DL and/or UL asymmetrically. In using the carrieraggregation technology, the setting of the component carriers may beprovided to a user equipment by a base station after RRC connectionprocedure. In this case, the RRC connection may mean that a radioresource is allocated to a user equipment based on RRC signalingexchanged between an RRC layer of the user equipment and a network viaSRB. After completion of the RRC connection procedure between the userequipment and the base station, the user equipment may be provided bythe base station with the setting information on the primary componentcarrier and the secondary component carrier. The setting information onthe secondary component carrier may include addition/deletion (oractivation/deactivation) of the secondary component carrier. Therefore,in order to activate a secondary component carrier between a basestation and a user equipment or deactivate a previous secondarycomponent carrier, it may be necessary to perform an exchange of RRCsignaling and MAC control element.

The activation or deactivation of the secondary component carrier may bedetermined by a base station based on a quality of service (QoS), a loadcondition of carrier and other factors. And, the base station may beable to instruct a user equipment of secondary component carrier settingusing a control message including such information as an indication type(activation/deactivation) for DL/UL, a secondary component carrier listand the like.

FIG. 6 is a conceptual diagram for dual connectivity (DC) between aMaster Cell Group (MCG) and a Secondary Cell Group (SCG).

The dual connectivity means that the UE can be connected to both aMaster eNode-B (MeNB) and a Secondary eNode-B (SeNB) at the same time.The MCG is a group of serving cells associated with the MeNB, comprisingof a PCell and optionally one or more SCells. And the SCG is a group ofserving cells associated with the SeNB, comprising of the special SCelland optionally one or more SCells. The MeNB is an eNB which terminatesat least S1-MME (S1 for the control plane) and the SeNB is an eNB thatis providing additional radio resources for the UE but is not the MeNB.

With dual connectivity, some of the data radio bearers (DRBs) can beoffloaded to the SCG to provide high throughput while keeping schedulingradio bearers (SRBs) or other DRBs in the MCG to reduce the handoverpossibility. The MCG is operated by the MeNB via the frequency of f1,and the SCG is operated by the SeNB via the frequency of f2. Thefrequency f1 and f2 may be equal. The backhaul interface (BH) betweenthe MeNB and the SeNB is non-ideal (e.g. X2 interface), which means thatthere is considerable delay in the backhaul and therefore thecentralized scheduling in one node is not possible.

FIG. 7a is a conceptual diagram for C-Plane connectivity of basestations involved in dual connectivity, and FIG. 7b is a conceptualdiagram for U-Plane connectivity of base stations involved in dualconnectivity.

FIG. 7a shows C-plane (Control Plane) connectivity of eNBs involved indual connectivity for a certain UE. The MeNB is C-plane connected to theMME via S1-MME, the MeNB and the SeNB are interconnected via X2-C(X2-Control plane). As FIG. 7a , Inter-eNB control plane signaling fordual connectivity is performed by means of X2 interface signaling.Control plane signaling towards the MME is performed by means of S1interface signaling. There is only one S1-MME connection per UE betweenthe MeNB and the MME. Each eNB should be able to handle UEsindependently, i.e. provide the PCell to some UEs while providingSCell(s) for SCG to others. Each eNB involved in dual connectivity for acertain UE owns its radio resources and is primarily responsible forallocating radio resources of its cells, respective coordination betweenMeNB and SeNB is performed by means of X2 interface signaling.

FIG. 7b shows U-plane connectivity of eNBs involved in dual connectivityfor a certain UE. U-plane connectivity depends on the bearer optionconfigured: i) For MCG bearers, the MeNB is U-plane connected to theS-GW via S1-U, the SeNB is not involved in the transport of user planedata, ii) For split bearers, the MeNB is U-plane connected to the S-GWvia S1-U and in addition, the MeNB and the SeNB are interconnected viaX2-U, and iii) For SCG bearers, the SeNB is directly connected with theS-GW via S1-U. If only MCG and split bearers are configured, there is noS1-U termination in the SeNB. In the dual connectivity, enhancement ofthe small cell is required in order to data offloading from the group ofmacro cells to the group of small cells. Since the small cells can bedeployed apart from the macro cells, multiple schedulers can beseparately located in different nodes and operate independently from theUE point of view. This means that different scheduling node wouldencounter different radio resource environment, and hence, eachscheduling node may have different scheduling results.

FIG. 8 is a conceptual diagram for radio protocol architecture for dualconnectivity.

E-UTRAN of the present example can support dual connectivity operationwhereby a multiple receptions/transmissions (RX/TX) UE in RRC_CONNECTEDis configured to utilize radio resources provided by two distinctschedulers, located in two eNBs (or base stations) connected via anon-ideal backhaul over the X2 interface. The eNBs involved in dualconnectivity for a certain UE may assume two different roles: an eNB mayeither act as the MeNB or as the SeNB. In dual connectivity, a UE can beconnected to one MeNB and one SeNB.

In the dual connectivity operation, the radio protocol architecture thata particular bearer uses depends on how the bearer is setup. Threealternatives exist, MCG bearer (801), split bearer (803) and SCG bearer(805). Those three alternatives are depicted on FIG. 8. The SRBs(Signaling Radio Bearers) are always of the MCG bearer and thereforeonly use the radio resources provided by the MeNB. The MCG bearer (801)is a radio protocol only located in the MeNB to use MeNB resources onlyin the dual connectivity. And the SCG bearer (805) is a radio protocolonly located in the SeNB to use SeNB resources in the dual connectivity.

Specially, the split bearer (803) is a radio protocol located in boththe MeNB and the SeNB to use both MeNB and SeNB resources in the dualconnectivity and the split bearer (803) may be a radio bearer comprisingone Packet Data Convergence Protocol (PDCP) entity, two Radio LinkControl (RLC) entities and two Medium Access Control (MAC) entities forone direction. Specially, the dual connectivity operation can also bedescribed as having at least one bearer configured to use radioresources provided by the SeNB.

FIG. 9 is a diagram for a general overview of the LTE protocolarchitecture for the downlink.

A general overview of the LTE protocol architecture for the downlink isillustrated in FIG. 9. Furthermore, the LTE protocol structure relatedto uplink transmissions is similar to the downlink structure in FIG. 9,although there are differences with respect to transport formatselection and multi-antenna transmission.

Data to be transmitted in the downlink enters in the form of IP packetson one of the SAE bearers (901). Prior to transmission over the radiointerface, incoming IP packets are passed through multiple protocolentities, summarized below and described in more detail in the followingsections:

-   -   Packet Data Convergence Protocol (PDCP, 903) performs IP header        compression to reduce the number of bits necessary to transmit        over the radio interface. The header-compression mechanism is        based on ROHC, a standardized header-compression algorithm used        in WCDMA as well as several other mobile-communication        standards. PDCP (903) is also responsible for ciphering and        integrity protection of the transmitted data. At the receiver        side, the PDCP protocol performs the corresponding deciphering        and decompression operations. There is one PDCP entity per radio        bearer configured for a mobile terminal.    -   Radio Link Control (RLC, 905) is responsible for        segmentation/concatenation, retransmission handling, and        in-sequence delivery to higher layers. Unlike WCDMA, the RLC        protocol is located in the eNodeB since there is only a single        type of node in the LTE radio-access-network architecture. The        RLC (905) offers services to the PDCP (903) in the form of radio        bearers. There is one RLC entity per radio bearer configured for        a terminal.    -   Medium Access Control (MAC, 907) handles hybrid-ARQ        retransmissions and uplink and downlink scheduling. The        scheduling functionality is located in the eNodeB, which has one        MAC entity per cell, for both uplink and downlink. The        hybrid-ARQ protocol part is present in both the transmitting and        receiving end of the MAC protocol. The MAC (907) offers services        to the RLC (905) in the form of logical channels (909).    -   Physical Layer (PHY, 911), handles coding/decoding,        modulation/demodulation, multi-antenna mapping, and other        typical physical layer functions. The physical layer (911)        offers services to the MAC layer (907) in the form of transport        channels (913).

The MAC (907) offers services to the RLC (905) in the form of logicalchannels (909). A logical channel (909) is defined by the type ofinformation it carries and are generally classified into controlchannels, used for transmission of control and configuration informationnecessary for operating an LTE system, and traffic channels, used forthe user data.

FIG. 10 is a diagram for signaling of buffer status and power-headroomreports.

The scheduler needs knowledge about the amount of data awaitingtransmission from the terminals to assign the proper amount of uplinkresources. Obviously, there is no need to provide uplink resources to aterminal with no data to transmit as this would only result in theterminal performing padding to fill up the granted resources. Hence, asa minimum, the scheduler needs to know whether the terminal has data totransmit and should be given a grant. This is known as a schedulingrequest.

The use of a single bit for the scheduling request is motivated by thedesire to keep the uplink overhead small, as a multi-bit schedulingrequest would come at a higher cost. A consequence of the single bitscheduling request is the limited knowledge at the eNodeB about thebuffer situation at the terminal when receiving such a request.Different scheduler implementations handle this differently. Onepossibility is to assign a small amount of resources to ensure that theterminal can exploit them efficiently without becoming power limited.Once the terminal has started to transmit on the UL-SCH, more detailedinformation about the buffer status and power headroom can be providedthrough the inband MAC control message, as discussed below.

Terminals that already have a valid grant obviously do not need torequest uplink resources. However, to allow the scheduler to determinethe amount of resources to grant to each terminal in future subframes,information about the buffer situation and the power availability isuseful, as discussed above. This information is provided to thescheduler as part of the uplink transmission through MAC controlelement. The LCID field in one of the MAC subheaders is set to areserved value indicating the presence of a buffer status report, asillustrated in FIG. 10.

Especially, to assist the scheduler in the selection of a combination ofmodulation-and-coding scheme and resource size M that does not lead tothe terminal being power limited, the terminal can be configured toprovide regular power headroom reports on its power usage. There is aseparate transmit-power limitation for each component carrier. Thus,power headroom should be measured and reported separately for eachcomponent carrier.

There are two different types of power-headroom reports defined for LTErelease 10, Type 1 and Type 2. Type 1 reporting reflects the powerheadroom assuming PUSCH-only transmission on the carrier, while theType-2 report assumes combined PUSCH and PUCCH transmission.

The Type-1 power headroom valid for a certain subframe, assuming thatthe terminal was really scheduled for PUSCH transmission in thatsubframe, is given by the following expression:

Power Headroom=P _(CMAX,c)−(P _(0,PUSCH) +α·PL_(DL)+10·log₁₀(M)+Δ_(MCS)+δ),  [Equation 1]

Where the values for M and F_(MCS) correspond to the resource assignmentand modulation-and-coding scheme used in the subframe to which thepower-headroom report corresponds. It can be noted that the powerheadroom is not a measure of the difference between the maximumper-carrier transmit power and the actual carrier transmit power. It canbe seen that the power headroom is a measure of the difference betweenP_(CMAX,c) and the transmit power that would have been used assumingthat there would have been no upper limit on the transmit power. Thus,the power headroom can very well be negative. More exactly, a negativepower headroom indicates that the per-carrier transmit power was limitedby P_(CMAX,c) at the time of the power headroom reporting. As thenetwork knows what modulation-and-coding scheme and resource size theterminal used for transmission in the subframe to which thepower-headroom report corresponds, it can determine what are the validcombinations of modulation-and-coding scheme and resource size M,assuming that the downlink path loss PL_(DL) and the term δ have notchanged substantially.

Type-1 power headroom can also be reported for subframes where there isno actual, PUSCH transmission. In such cases, 10·log 10 (M) and Δ_(MCS)in the expression above are set to zero:

Power Headroom=P _(CMAX,c)−(P _(0,PUSCH) +α·PL _(DL)+δ).  [Equation 2]

This can be seen as the power headroom assuming a default transmissionconfiguration corresponding to the minimum possible resource assignment(M=1) and the modulation-and-coding scheme associated with Δ_(MCS)=0 dB.

Similarly, Type-2 power headroom reporting is defined as the differencebetween the maximum per-carrier transmit power and the sum of the PUSCHand PUCCH transmit power respectively, once again not taking intoaccount any maximum per-carrier power when calculating the PUSCH andPUCCH transmit power.

Similar to Type-1 power headroom reporting, the Type-2 power headroomcan also be reported for subframes in which no PUSCH and/or PUCCH istransmitted. In that case a virtual PUSCH and or PUCCH transmit power iscalculated, assuming the smallest possible resource assignment (M=1) andΔ_(MCS)=0 dB for PUSCH and Δ_(Format)=0 for PUCCH.

For the uplink, the power availability, or power headroom is defined asthe difference between the nominal maximum output power and theestimated output power for UL-SCH transmission. This quantity can bepositive as well as negative (on a dB scale), where a negative valuewould indicate that the network has scheduled a higher data rate thanthe terminal can support given its current power availability. The powerheadroom depends on the power-control mechanism and thereby indirectlyon factors such as the interference in the system and the distance tothe base stations.

Information about the power headroom is fed back from the terminals tothe eNodeB in a similar way as the buffer-status reports—that is, onlywhen the terminal is scheduled to transmit on the UL-SCH. Type-1 reportsare provided for all component carriers simultaneously, while Type-2reports are provided for the primary component carrier only.

A power headroom report can be triggered for the following reasons:

-   -   Periodically as controlled by a timer.    -   Change in path loss, since the last power headroom report is        larger than a (configurable) threshold.    -   Instead of padding (for the same reason as buffer-status        reports).

It is also possible to configure a prohibit timer to control the minimumtime between two power-headroom reports and thereby the signaling loadon the uplink.

FIG. 11 is a conceptual diagram for one of radio protocol architecturefor dual connectivity.

The UE transmits Buffer Status Report (BSR) to the eNB to assist the eNBin allocating the uplink radio resources to the different UEs byindicating the amount of data buffered across the UE's PDCP and RLCmemory. The BSR shall be triggered by the timers and the events asdescribed in the above Prior Art. For example, there are timers, i.e.,retxBSR-Timer and periodic BSR-Timer, which triggers BSR upon timerexpiry.

However, in LTE Rel-12, a new study on dual connectivity, i.e. UE isconnected to both MeNB (1101) and SeNB (1103), as shown in FIG. 11. Inthis figure, the interface between MeNB (1101) and SeNB (1103) is calledXn interface (1105). The Xn interface (1105) is assumed to be non-ideal;i.e. the delay in Xn interface could be up to 60 ms, but it is notlimited thereto.

To support dual connectivity, one of the potential solutions is for theUE (1107) to transmit data to both MeNB (1101) and SeNB (113) utilizinga new RB structure called dual RLC/MAC scheme, where a single RB has onePDCP-two RLCs-two MACs for one direction, and RLC/MAC pair is configuredfor each cell, as shown in FIG. 11. In this figure, BE-DRB (1109) standsfor DRB for Best Effort traffic.

In this case, the UE can perform the UL transmission through MeNB (1101)and SeNB (1103), which are located in different areas. Since each ULtransmission to MeNB (1101) and SeNB (1103) will experience differentradio environment, e.g., pathloss, it is desirable that the eNB knowsthe power headroom of MCG and SCG independently. However, if the UEreports the power headroom of each cell to the corresponding eNB, eacheNB would estimate the power headroom of the UE incorrectly because theMeNB (1101) does not know the PHR for SeNB (1103) and vice versa. Basedon the provided PHR from the UE, each eNB may schedule more uplinkresources for the UE. Accordingly, in the UE side, the sum oftransmission power on UL-SCH across the MCG and SCG would exceed themaximum transmit power.

FIG. 12 is a conceptual diagram for a problematic case in dualconnectivity.

For example, the nominal UE maximum transmit power is P-MAX and the UEcalculates that PH for the one cell of MCG and one cell of SCG as PH-Mand PH-S, respectively, and sends them to the corresponding MeNB andSeNB.

Note that the total power headroom the UE is PH-T, which cannot bededuced solely from the PH-M or PH-S. When each eNB receives those PHR,the MeNB analyzes that there is PH-M remaining power resource for theUE, and the SeNB analyzes that there is PH-S remaining power resourcefor the UE. As a result, the MeNB and the SeNB allocates additionalresources based on PH-M and PH-S so that additional power PH-M+PH-Swould be required for the UE, which exceeds actual total PH of the UE(PH-T).

FIG. 13 is a conceptual diagram for power headroom reporting accordingto embodiments of the present invention.

The dual connectivity means that the UE can be connected to both a firstbase station and a second base station at the same time. The first basestation may be a Master eNode-B (MeNB) and the second base station maybe a Secondary eNode-B (SeNB), and vice versa.

A MCG is a group of serving cells associated with the MeNB, comprisingof a PCell and optionally one or more SCells. And a SCG is a group ofserving cells associated with the SeNB, comprising of the special SCelland optionally one or more SCells. The MeNB is an eNB which terminatesat least S1-MME (S1 for the control plane) and the SeNB is an eNB thatis providing additional radio resources for the UE but is not the MeNB.

With dual connectivity, some of the data radio bearers (DRBs) can beoffloaded to the SCG to provide high throughput while keeping schedulingradio bearers (SRBs) or other DRBs in the MCG to reduce the handoverpossibility. The MCG is operated by the MeNB via the frequency of f1,and the SCG is operated by the SeNB via the frequency of f2. Thefrequency f1 and f2 may be equal. The backhaul interface between theMeNB and the SeNB is non-ideal, which means that there is considerabledelay in the backhaul and therefore the centralized scheduling in onenode is not possible.

In this invention, to prevent the eNB from over-allocation of uplinkresources to the UE with a dual connectivity, if the UE has a dualconnectivity with a first base station and a second base station, whenthe UE reports Power Headroom (PH) of first cell to an base station ofthe first cell, the UE adds additional information that indicates the PHof the UE in the same PHR. Additionally, the UE adjusts the PH of eachcell taking into consideration of the PH of the UE and transmits them toeach base station.

When the PHR is triggered, if the UE is connected to the first basestation and the second base station, the UE firstly calculates the PHfor each cell using the nominal UE maximum transmit power (P_(CMAX,c))as in the prior art.

The UE may obtain information related to a power headroom (PH) statusfor the second BS (S1301) or information related to a PH for the firstBS (S1303).

Desirably, the information may comprise a ratio of a PH for the secondBS (PH-S) to a PH for the first BS (PH-M). The information may comprisea ratio of a PH for the first BS (PH-M) to the PH of activated cells ofthe UE (PH-T). Or, the information may comprise a ratio of a PH for thesecond BS (PH-S) to the PH of activated cells of the UE (PH-T).

For example, the current a PH for the first BS (PH-M) and a PH for thesecond BS (PH-S) are 10 and 20. If the information comprises a ratio ofa PH for the second BS to a PH for the first BS, the UE may calculatethe ratio as PH-S/PH-M or PH-M/PH-S for the first BS and the second BS,respectively, i.e., 2 or ½.

If the information may comprise a ratio of a PH for the first BS (PH-M)to the PH of activated cells of the UE (PH-T), then the UE may calculatethe ratio as PH-M/PH-T and PH-S/PH-T for the first BS and the second BS,i.e., 2 and 4, respectively.

When the UE calculates the ratio using the PH-M, PH-S, and PH-T, the UEmay transmit the ratio along with the PH-M and PH-S to the MeNB andSeNB, respectively, in the same PHR.

The UE may transmit the ratio as PH-S/PH-M (i.e., 2) or PH-M/PH-T (i.e.,2) to the first base station with PH of activated cells of the UE(S1305).

The UE may transmit the ratio as PH-M/PH-S (i.e., ½) or PH-S/PH-T (i.e.,4) to the second base station with PH of activated cells of the UE(S1307).

When the UE transmits the ratio to the corresponding base station, thefirst base station analyzes that the UE reports PHR to the second eNBwith the PH multiplied by the RATIO-PH. In the above example, when UEtransmits the PH-M=10 to the first base station and theratio=PH-S/PH-M=2, then the first base station analyzes that the UEtransmits the PH-S=20 to the second base station. If the UE transmitsthe PH-M=10 and the ratio=PH-S/PH-M=2 to the first base station, thenthe first base station analyzes that the PH of the UE is 5 and knowsthat the UE sends the PH of the one of cells served by the second basestation to the second base station.

By the way, in the step of S1301 and S1303, desirably, the informationmay comprise scheduling information for the second BS. Or, theinformation may comprise scheduling information for the first BS.

Desirably, the scheduling information may indicate whether the UEreceived the UL grant for the second BS when the UE transmits thescheduling information to the first base station along with the PH ofactivated cells of the UE. On the other hands, the schedulinginformation may indicate whether the UE received the UL grant for thefirst BS when the UE transmits the scheduling information to the secondbase station along with the PH of activated cells of the UE.

Desirably, the scheduling information may indicate whether the UEtransmits the PH for one of cells served by the second base station tothe second base station when the UE transmits the scheduling informationto the first base station along with the PH of activated cells of theUE. On the other hands, the scheduling information may indicate whetherthe UE transmits the PH for one of cells served by the first basestation to the first base station when the UE transmits the schedulinginformation to the second base station along with the PH of activatedcells of the UE.

Desirably, the scheduling information may indicate whether the UEtransmits a larger/smaller PH for one of cells served by the second basestation to the second base station when the UE transmits the schedulinginformation to the first base station along with the PH of activatedcells of the UE. On the other hands, the scheduling information mayindicate whether the UE transmits a larger/smaller PH for one of cellsserved by the first base station to the first base station when the UEtransmits the scheduling information to the second base station alongwith the PH of activated cells of the UE.

Desirably, the scheduling information may indicate whether the UE'soverall PH of the UE is less or equal to the PH for one of cells servedby the first base station or not. Or the scheduling information mayindicate whether the UE's overall PH of the UE is less or equal to thePH for one of cells served by the second base station or not.

When the UE reports the PH of cells served by each base station (thefirst base station and the second base station) to the correspondingbase station, the UE sends the scheduling information that indicates theoverall status of PH of the UE along with the PH in the same PHR (S1305& S1307).

Upon receiving the scheduling information from the UE that indicates theoverall status of PH of the UE along with the PH in the same PHR, thecorresponding base station analyzes whether the actual PH of the UE issmaller or equal to the received PH or not.

FIG. 14 is a conceptual diagram for power headroom reporting accordingto embodiments of the present invention.

When the UE reports the PH of cells served by each base station (thefirst base station and the second base station) to the correspondingbase station, the UE may adjusts the PH using the Power Headroom per UE(PH-T).

In detail, the UE adjusts the PH-M and PH-S using weight factors a firstweight factor (W_(M)) and a second weigh factor (W_(S)) so that the sumof PH-M and PH-S is smaller than the PH-T.

For this purpose, the UE may obtain information related to a PH for thefirst base station (S1401) and a PH for the second base station (S1403).The UE may determine the first weight factor for the first base stationand a second weigh factor for the second base station (S1407) if sum ofa power headroom (PH) status for the first base station and a PH for thesecond base station is more than a PH of activated cells of the UE(S1405).

Desirably, the first weigh factor may be determined by using: a value ofthe PH for the first base station over a value of the PH of activatedcells of the UE. And the second weigh factor is determined by using: avalue of the PH for the second BS over a value of the PH of activatedcells of the UE.

The UE adaptively calculates the weight factor as W_(M)=PH-M/(PH-M+PH-S)and W_(S)=PH-S/(PH-M+PH-S) for the first base station and the secondbase station, respectively. For example, if the current PH-M and PH-Sare 20 and 10, respectively, and if the PH-T is 5, then the UE adjuststhe PH-M and PH-S as PH-T×W_(M)=5×10/(10+20)=5/3 andPH-S×W_(S)=5×20/(10+20)=10/3.

Desirably, the first weight factor and the second weight factor may betransmitted by at least the first base station or the second basestation using a MAC/RRC signaling.

Alternatively, the UE uses the fixed weight values of W_(M) and W_(S)where the sum of W_(M) and W_(S) equals to 1. For example, if W_(M) andW_(S) are 0.7 and 0.3 respectively, and the current PH-T is 10, then theUE adjusts the PH-M and PH-S as PH-T×W_(M)=10×0.7=7 andPH-S×W_(S)=10×0.3=3.

Alternatively, the UE uses the fixed weight values of W_(M) and W_(S)where the sum of W_(M) and W_(S) does not necessarily equal to 1. Thoseweight values are used to scale down the PH of each cell. The UE can beconfigured with the fixed weight values from the the first base stationor the second base station using a MAC/RRC signaling.

For example, if W_(M) and W_(S) are 0.4 and 0.5 respectively, and thecurrent PH-M and PH-S are 20 and 10, then the UE adjusts the PH-M andPH-S as PH-M×W_(M)=20×0.4=8 and PH-S×W_(S)=10×0.5=5.

The UE may reduce size of PH for at least one cell of the first BS byusing the first weight factor (S1409) and report the reduced PH for atleast one cell of the first BS to the first BS (S1413).

The UE may reduce size of PH for at least one cell of the second BS byusing the second weight factor (S1411) and report the reduced PH for atleast one cell of the second BS to the second BS (S1415).

FIG. 15 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 15 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 15, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transceiver (135) and controls it.The apparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 15 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 15 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The embodiments of the present invention described herein below arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

1. A method for a user equipment (UE) operating in a wireless communication system comprising a first base station (BS) and a second BS, the method comprising: obtaining information related to a power headroom (PH) for the second BS; obtaining PH of activated cells of the UE; and transmitting, to a first BS, the information related to the PH for the second BS and the PH of activated cells of the UE.
 2. The method according to claim 1, wherein the information comprises a ratio of a PH for the second BS to a PH for the first BS.
 3. The method according to claim 1, wherein the information comprises a ratio of a PH for the first BS to the PH of activated cells of the UE.
 4. The method according to claim 1, wherein the information comprises scheduling information for the second BS.
 5. The method according to claim 4, wherein the scheduling information indicates whether the UE received the UL grant for the second BS or not.
 6. The method according to claim 4, wherein the scheduling information indicates whether the UE transmits the PH of the second BS to the second BS or not.
 7. A user equipment (UE) in a wireless communication system comprising a first base station (BS) and a second BS, the UE comprising: an RF (radio frequency) module; and a processor configured to control the RF module, wherein the processor is configured to obtain information related to a power headroom (PH) for the second BS, to obtain PH of activated cells of the UE, and to transmit to a first BS, the information related to the PH for the second BS and the PH of activated cells of the UE.
 8. The UE according to claim 7, wherein the information comprises a ratio of a PH for the second BS to a PH for the first BS.
 9. The UE according to claim 7, wherein the information comprises a ratio of a PH for the first BS to the PH of activated cells of the UE.
 10. The UE according to claim 7, wherein the information comprises scheduling information for the second BS.
 11. The UE according to claim 10, wherein the scheduling information indicates whether the UE received the UL grant for the second BS or not.
 12. The UE according to claim 10, wherein the scheduling information indicates whether the UE transmits the PH of the second BS to the second BS or not. 